A grid-connected inverter is a power conversion device widely used in such fields as wind power, solar power and energy storage apparatus, and the trend is that its use is gradually on the increase. Particularly, a medium or large capacity power conversion apparatus of more than several kW is gradually expanded in its area of use for grid stability in response to increase in use of new renewable energy. A conventional grid-connected inverter is controlled by a spatial vector PWM (Pulse Width Modulation) method using an offset voltage, and this method is advantages of improving THD (Total Harmonic Distortion) of output current.
However, the spatial vector PWM (Pulse Width Modulation) method suffers from disadvantages of degraded system efficiency due to increased switching loss, because all switches of power semiconductors are switched while constantly maintaining an offset voltage.